SUBSTRATE-SPECIFICITY OF AMINOPEPTIDASE EY FROM HENS (GALLUS-DOMESTICUS) EGG-YOLK

1. Aminopeptidase Ey, purified from the egg yolk of the hen (Gallus ga llus domesticus), was studied for its specificity against oligopeptide s at pH 7.5. The enzyme has a broad specificity for amino acid residue s at P1 position. 2. The enzyme hydrolyzed N-terminal Xaa-Pro bonds in chicken brain peptide (Leu-Pro-Leu-Arg-PheNH2), substance P fragment 1-4 (Arg-Pro-Lys-Pro) and bradykinin fragment 1-5 (Arg-Pro-Pro-Gly-Phe ), but did not hydrolyze substance P (Arg-Pro-Lys-Pro-Gln-Gln-Phe-Phe- Gly-Leu-MetNH2) or bradykinin (Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg). 3 . The enzyme released proline from Pro-Phe-Gly-Lys, while it was unabl e to release proline from melanocyte, stimulating the hormone release- inhibiting factor (Pro-Leu-GlyNH2) and schistoFMRF-amide (Pro-Asp-Val- Asp-His-Val-Phe-Leu-Arg-PheNH2).